1. Field of the Invention
The present invention relates to a charging type electronic timepiece having a voltage-varying power supply in the form of an electric storage device such as a secondary battery or a high-capacitance capacitor which is charged by a solar battery or other electric generating means.
2. Description of the Related Art
The power supply (electric storage device) of such a charging type electronic timepiece has a voltage which varies depending on the state of charging. Also, the charging action is not regularly performed, so that the timepiece might possibly come to a stop due to little or substantially no charging under poor conditions, for example, in a long-term low illuminance condition in the case of using the solar battery. Usually, as the charged quantity of electricity increases the power-supply voltage goes up. Thus, some timepieces of such a type tried as hard as possible to avoid troubles which may be caused by a stop of the timepiece, by using the electric storage device voltage (power-supply voltage) not merely for the timepiece display action but also for providing the user with information on the state of timepiece power supply and on the history of stop or information on a short of charging.
A first conventional example of such a charging type timepiece is disclosed in Japanese Patent Pub. No. Hei 7-89154(KOKOKU). This technique allows an ordinary action (1 sec. step hand driving) when the power supply has a sufficient charged quantity (power-supply voltage) but allows a first modulated hand driving action (2 sec. step hand driving) serving as a charging alarm when the charged quantity is ready to run short. Then, the arrangement is such that when the timepiece has stopped due to a short of the charged quantity, two types of alarm displays are provided by modulating the hand driving action differently from the first modulated hand driving action or by allowing a second modulated hand driving action as a stop alarm, in order to warn the user that a stop history occurred even though the hand driving has been restarted as a result of the subsequent restoration of the charged quantity and therefore that the indicated time is slow.
A second conventional example of the charging type timepiece is disclosed in Japanese Patent No. 2534484. This technique aims to achieve a power saving by stopping the hand driving in case the charged quantity has dropped to an extent which is insufficient to keep the timepiece hand driving by the step motor but is sufficient to keep the timepiece circuit action requiring a small amount of power consumption. Then, the arrangement is such that the circuit-based measurement is made of the duration by the hand driving stop so that when the hand driving has again become possible due to the subsequent recovery of the potential through recharging before reaching the potential causing a stop of oscillation, the pulse motor is rapidly forwarded in accordance with the result of the above measurement to allow the stopped hands to rapidly catch up with the correct time.
However, these prior art publication have Insufficient aspects for the improvement in spite of their respective advantages. More specifically, the first conventional example is very excellent in that it allows the timepiece to provide not only the charge alarm display but also the stop alarm display indicative of possession of a history of stop including the case of oscillation stop, but it lacks a consideration for the recovery of time after the restoration of the power-supply voltage.
The second conventional example is excellent in that it substantially released the user from cumbersome time adjusting operation through the return to the correct time of the timepiece itself, but it does not perform any return to the correct time in case the voltage has further dropped resulting in the oscillation stop. It also lacks a consideration for a positive notice to the user on the fact that the displayed time is not correct time.